1. Field of the Invention
The present invention relates to diapers (or napkins), particularly discardable diapers, comprising a flexible and impermeable support sheet, a flexible and permeable upper sheet joined to the support sheet over at least a portion of the periphery of the diaper. A pad of absorbent material is placed between the upper sheet and the support sheet and elastic means positioned over at least a portion of the periphery of the diaper designed to be applied elastically onto the body of a user of this diaper.
2. Description of the Prior Art
Numerous diapers are now found provided with elastic members at the level of the crotch designed to form a barrier around the thighs of the user of the diaper. Such diapers have different shapes; thus, they may be rectangular with longitudinal edges, as the case may require, folded back to reduce the width at the crotch or have a cut-out at the level of this crotch in order to reduce the width of the diaper and thus to constitute a so-called anatomical shape.
These diapers provided with elastic elements at the crotch are generally well adapted to the body of the user and do not show leakages around the thighs at least when they are not saturated with liquid or poorly positioned.
However, leakages frequently occur around the waists of babies according to the position of the latter. Such leakages are associated with the morphology of the baby, who does not have a muscular abdominal belt. In spite of all the precautions which can be taken on the placing in position of the napkin, the latter, which is capable of being distorted at the level of the waist, begins, after a certain number of changes in position of the baby, to gape at the level of the waist of the latter which thus results in risk of leakages in the following cases:
-Direct leakages especially in reclining position. The flow rate of the urination, generally being very much greater at the level at which the urine flows through the permeable upper sheet, the urinary liquid escapes at the spot where the complete change is not tight. This type of leakage can also occur on occasional pressure exerted on the absorbent material of the pad when the latter is close to saturation;
-Direct leakages by directional orientation of the urination stream towards the place at the waist of the infant where the diaper has a tendency to gape, which is the case with boys;
-Leakage by capillary pumping when an undergarment of hydrophilic material slips between the skin and the diaper which gapes at the level of the waist.
To avoid such leakages and to apply the corresponding portion of the diaper better to the waist of the user, certain diapers have been provided with elastic members in the form of strips, tapes or threads fixed to at least a part of the width of the diaper and at the border of the latter between the support sheet and the top sheet. Such diapers are described in patents FR-A-82 04 390 and 84 08 289.
However, these improvements associated with a more hermetic application of the diaper to the user do not make any contribution to provide means intended to place the inner space of the diaper in communication with the outside and in this manner to permit the passage of gaseous fluids and, thus, to ventilate the inside of the diaper to contribute to the comfort of the user.
In the prior art there are found diapers which, to arrange means of communication of their inner space with the outside when the diaper is worn, provide perforations or microperforations formed on the support sheet which normally is completely impermeable. It appears, however, that in the case of microperforations, the flow rate of gaseous fluid that the diaper can exchange with the outside is relatively low. In the case of perforations, the fluid tightness of the diaper with respect to liquid leakages is compromised, the permeability of the support sheet being too degraded.